1. Field of the Invention
The present invention generally relates to an apparatus capable of preventing obstructive sleep apnea (OSA) and a method for maintaining a negative oral pressure and collecting liquid. More particularly, the present invention relates to a negative-pressure oral apparatus disposed in the oral cavity and capable of providing the oral cavity with a negative pressure to prevent obstructive sleep apnea (OSA) and snoring and expelling a liquid in the oral cavity to prevent liquid leakage or contamination and a method for maintaining a negative oral pressure and collecting liquid.
2. Description of the Prior Art
Obstructive sleep apnea (OSA) happens when the muscles in the oral cavity and the back of the gullet of a person are relaxed so that the person stops breathing intermittently for hundreds of times through the night. Each time may last as long as one minute. FIG. 1A shows the normal breathing condition of a sleeping person. In FIG. 1A, the upper respiratory airway 10 is kept unobstructed. FIG. 1B shows the muscles in the oral cavity and the back of the gullet of a person are relaxed when he is sleeping so that the upper respiratory airway 10 is narrowed to cause upper airway resistance syndrome (UARS) and snoring. In FIG. 1C, the muscles in the oral cavity and the back of the gullet of a person are relaxed when he is sleeping so that the upper respiratory airway 10 is blocked up to cause obstructive sleep apnea (OSA).
It is estimated that ten percent of the people in the world suffer from OSA. However, only a few of them are treated. Those with OSA are faced with life-threatening situations such as higher death rate, higher hypertensive risk and higher myocardial infarction (MI) risk. The survival rate of the untreated patients with apnea-hypopnea index (AHI) larger than 20 is lowered by 36 percent than the survival rate of the untreated patients with AHI smaller than 20 in eight years. The ratio of hypertension rate of the patients with respiration disorder index (RDI) of 5 to that of those people without OSA is 2:1. The ratio of hypertension rate of the patients with respiration disorder index (RDI) of 25 to that of those people without OSA is 5:1. The possibility of a recurrence of hypertension of the patients with OSA is 23 times the possibility of a recurrence of hypertension of the people without OSA. The vehicle accident rate of the untreated patient with OSA is 7 times the vehicle accident rate of the people without OSA and it is 12 times for the vehicle accident rate per mile.
Please refer to FIG. 2, which is a schematic diagram showing a constant positive airway pressure (CPAP) machine 11 used for treating OSA. The CPAP machine 11 is widely used for treating OSA by providing the patient with a constant positive airway pressure through a mask so that the upper respiratory airway is kept unobstructed. Even though the respiratory airway is kept unobstructed, it makes the patient uncomfortable because the high-pressure air flows into the upper respiratory airway. Therefore, the patient compliance rate is as low as 40 to 50%. Alternatively, OSA can also be treated by using soft tissues removal surgery, bone surgery or oral appliances.
In U.S. Pat. No. 6,494,209, an oral device for treatment of obstructive sleep disorders is disclosed. It is characterized in that the tongue is protected and separated from the teeth when the device is in use. The oral device further comprises a tongue shaped cavity for receiving the tongue. Moreover, a negative pressure is applied directly on the soft tissues of the tongue to hold the tongue within the cavity. However, such negative pressure may cause damage to the soft tissues of the tongue.
Moreover, in U.S. Pat. No. 5,957,133, an oral appliance with a negative air supply for reducing sleep apnea and snoring is provided, in which a negative air pressure source expels the air from the oral cavity to pull the tongue and the palate forward so that the upper airway is unobstructed. However, the oral appliance occupied a lot of the oral cavity and is vomitive. Meanwhile, the aforesaid patents do not teach how to effectively remove and store excess saliva.